EPSC2013: Get ready for Rosetta’s wake-up call with activity schedule for target comet

September 13, 2013

EPSC2013: Get ready for Rosetta’s wake-up call with activity schedule for target comet

After a journey of almost ten years, the Rosetta mission has just a few months left to wait before beginning its rendezvous with a time capsule. Comet 67P/Churymov-Gerasimenko is a dirty snowball of ice and dust that preserves material from the formation of the Solar System 4.5 billion years ago. During 2014, the European Space Agency’s most ambitious mission to date will both start to orbit the comet’s nucleus and deploy a small laboratory of scientific instruments, Philae, to dock with the comet’s surface. To aid Rosetta in safely achieving its task, an international group of scientists back on Earth are using ground-based telescopes and computer models to understand the behaviour of the comet as it approaches the Sun and begins to form its tail. Their findings have been presented this week at the European Planetary Science Congress (EPSC) 2013 at University College London.

“For two or three orbits now, our community has been observing the comet to determine the shape of the nucleus, the angle at which it spins on its axis and how its activity varies as it orbits the Sun. All of this information is vital for the planning of Rosetta’s orbit and Philae’s delivery,” said Jessica Agarwal of the Max Planck Institute for Solar System Research (MPS).

“At this meeting, we have discussed everything from the make-up of the surface layer of the nucleus to the dust production rates, size and velocity of the particles emitted, the way the comet interacts with the solar magnetic environment… There are a lot of things we need to know!” added Matt Taylor, ESA’s Project Scientist for the Rosetta Mission.

Jean-Baptiste Vincent (MPS) has used images and modelling to study the development of gas jets as the comet becomes active. “We need to understand the formation and evolution of dust coma structures at all scales: from tiny filaments only visible close to the surface of the nucleus, to large structures extending tens of thousands of kilometres in the coma. Comet 67P appears to behave in a very consistent way, at least over the last two orbits. The southern hemisphere is more active than the northern and there are three major active regions from where gas jets evolve, which can eject dust particles at around 50 kilometres per hour.”

To safeguard the spacecraft during its long, cold journey through deep space, Rosetta was placed into hibernation in 2011. Research by a group led by Colin Snodgrass and Cecilia Tubiana of MPS suggests that 67P will start emitting gas and dust by March 2014, earlier than expected and just two months after the spacecraft receives its wakeup call on Monday 20 January 2014.

The scientists have based their predictions on 31 sets of images showing the comet at different points during its orbit. The images were recorded between 1995 and 2010 with telescopes including the Very Large Telescope (VLT) at the European Southern Observatory (ESO). By subtracting successive images to remove the starry background and making the comet stand out, they were able to study changes in brightness and hence the activity levels of the comet was at different points in its orbit.

“For the first time, we have a meaningful comparison of all data sets so that we can reconstruct the activity of the comet as it moves around the Sun,” said Snodgrass. “The results were something of a surprise.”

Scientists had estimated that the comet would start to form is tail at distance of around 450 million kilometres from the Sun, when it would become warm enough for water ice to sublimate. Instead, it became active much further out — at 650 million kilometres.

“Water will still be frozen solid at that distance from the Sun. Some other gas must be responsible for this earlier activity that we’ve observed,” said Tubiana.

IMAGES AND ANIMATIONS

Image of 67P/Churyumov-Gerasimenko acquired in February 2009, processed using a numerical filter. Structures visible in the image are signatures of regions of enhanced activity on the nucleus surface. Credit: J-B Vincent/MPS/GP Tozzi/L Lara/Z-Y Lin

Dust coma of 67P at a distance of 187 million kilometres from the Sun, shortly before the comet’s closest approach. Image acquired on 18 Feb. 2009. The image (top left) is presented as processed through various numerical filters to enhance the visibility of the jets. J-B Vincent/MPS/GP Tozzi/L Lara/Z-Y Lin

Movie showing modelled dust jets of comet 67P/C-G as they would be observed by the OSIRIS WAC camera on board Rosetta. Credit: J-B Vincent/MPS

Still from movie showing modelled dust jets of comet 67P/C-G as they would be observed by the OSIRIS WAC camera on board Rosetta. Credit: J-B Vincent/MPS

EPSC is the major European meeting on planetary science. EPSC 2013 is taking place at University College London (UCL) from Sunday 8 September to Friday 13 September 2013. It is the first time that the Congress has been held in the UK. The 2013 programme includes around 75 sessions and workshops. Details of the Congress and a full schedule of EPSC 2013 scientific sessions and events can be found at the official website: http://www.epsc2013.eu/

EPSC 2013 is organised by Europlanet, UCL and Copernicus Meetings and the event is sponsored by the UK Space Agency, UCL, Astrium and the Science and Technology Facilities Council.

To celebrate EPSC coming to London, a ‘Festival of the Planets’ has been organised across the Capital in collaboration with partners including the Baker Street Irregular Astronomers, the Bloomsbury Theatre, the British Astronomical Association, the British Interplanetary Society, the Natural History Museum, the Open University, Queen Mary University of London, the Royal Astronomical Society, Royal Museums Greenwich and University College London. More information about the events can be found at:

Europlanet is a network of planetary scientists, whose aim is to bring together the disparate European community so that Europe can play a leading role in space exploration. Europlanet’s activities complement the mission activities of the European Space Agency through field work at planetary-analogue terrains on Earth, laboratory measurements, computer modelling and observations from ground-based telescopes. Founded in 2002 and funded by the European Commission from 2005-2012, Europlanet has evolved into a community-based organisation that will carry on this work and plan for future missions and mission support.

www.europlanet-eu.org

About UCL (University College London)

Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender and the first to provide systematic teaching of law, architecture and medicine.

UCL is among the world’s top universities, as reflected by its performance in a range of international rankings and tables. According to the Thomson Scientific Citation Index, UCL is the second most highly cited European university and the 15th most highly cited in the world.

UCL has nearly 27,000 students from 150 countries and more than 9,000 employees, of whom one third are from outside the UK. The university is based in Bloomsbury in the heart of London, but also has two international campuses – UCL Australia and UCL Qatar. Its annual income is more than £800 million.